nx-match: Serialize match on IP TTL even when outputting OXM.
The 'oxm' parameter to nxm_put_ip() indicates whether NXM or OXM code
points should be used in cases where both exist. It shouldn't cause
matches to be dropped entirely, since that changes the meaning, but that's
what was done here for matches on the IP (v4 or v6) TTL. This commit
fixes the problem.
Signed-off-by: Ben Pfaff <blp@nicira.com> Acked-by: Justin Pettit <jpettit@nicira.com>